This invention relates broadly to surgical instruments. More particularly, this invention relates to a surgical snare instrument for excising polyps. Preferably, the instrument includes a coupling member that may increase the ability to actuate the snare.
Polypectomy snare instruments are used for the endoscopic removal of hypertrophic tissue growths within a body cavity, and particularly within the colon. Polypectomy snare instruments generally include an elongate tubular member, such as a catheter sheath, a shaft extending through the tubular member, an elastic wire forming a snare (loop) at the distal end of the shaft, and a handle for moving the shaft distally and proximally within the tubular member. The snare can be opened by moving the snare beyond the distal end of the sheath, and closed by retraction of the snare into the tubular member, each affected by movement of the shaft relative to the sheath.
In operation, a physician introduces the distal end of the instrument, with the snare of the snare instrument in a retracted position, through the working channel of an endoscope until the sheath begins to extend out of the distal end of the endoscope. The physician then directs an assistant, who has control of the handle of the snare instrument, to open the snare. The assistant accomplishes this function by moving two portions of the handle relative to each other. The physician then advances and retracts the sheath into and out of the endoscope, while applying torque to some portion of the instrument to position the snare loop over and around a polyp. Once the snare loop is positioned around the polyp, the physician orders the assistant to close the snare around the polyp. Then, the physician or assistant energizes a source of electrocautery current coupled to the shaft to desiccate, sever, and cauterize the polyp. Finally, the polyp is removed by withdrawing the snare (or, in some cases, the polyp is retrieved by use of another instrument such as a biopsy forceps). In a variation of the procedure, the physician uses suction applied to a channel of the endoscope to remove the polyp or to hold it to the end of the endoscope.
Prior art snare instruments have several problems. First, it is difficult for the physician to precisely position the snare because the physician relies on gripping the small, slippery sheath over the shaft near where the sheath enters the endoscope handle. Typically, it is necessary for the physician to repeatedly push, pull, and torque the sheath and the shaft of the instrument in order to achieve the desired position with the snare around the polyp. Second, the prior art instruments are not capable of efficient steering, because the shaft which is generally used is a cable having low torsional stiffness, and, is not usually free of camber or xe2x80x9csetxe2x80x9d. The result of these defects is that when the instrument is used in a tightly-flexed endoscope, the distal end of the snare does not respond directly to torsional input on the shaft where it enters the endoscope handle; i.e., rather than directly responding to torsional input from the physician, the shaft stores the torsional force and upon reaching a threshold, uncontrollable rotationally whips to release the force. Third, while several attempts have been made at providing a snare instrument with a handle adapted to more adeptly steer the snare, most of such prior art instruments do not specifically allow for rotating the snare to position it relative to the polyp. Rather, the physician must rotate the shaft of the instrument by tightly gripping and rotating the sheath where it enters the endoscope to try to maneuver the snare over the polyp. In addition, in the several prior art devices specifically adapted for rotational control, e.g., U.S. Pat. No. 5,066,295 to Kozak et al. and U.S. Pat. Nos. 3,955,587; 4,256,113; and 4,294,254 to Chamness et al., the rotational control function is placed in the handle at the proximal end of the instrument. This handle then controls the extension and retraction of the snare loop as well as the rotation of the snare loop. However, this handle is typically held by the assistant, so the physician must orally direct the assistant to coordinate the handle controls while the physician moves the jacket in and out of the endoscope. As a result, these instruments have not been widely accepted by physicians.
The invention provides a snare instrument which permits the physician to control all aspects of positioning the snare loop relative to the polyp, while allowing the assistant to perform the cauterizing and severing of the polyp. The snare instrument provides the physician the means for advancing and retracting the distal end of the snare instrument through the endoscope, as well as rotating the snare, and provides the assistant the means for extending and retracting the snare loop from the sheath of the snare instrument.
As described in detail below, a surgical snare instrument is provided. The snare instrument includes an elongate flexible tubular sheath, a flexible shaft extending through and axially movable relative to the sheath, a snare coupled to or formed at the distal end of the shaft, and a system to move the shaft, and consequently the snare, relative to the sheath. According to several embodiments of the invention, the system for moving the shaft relative to the sheath includes a first (physician""s) handle capable of controlling the position of the snare, and a second (assistant""s) handle proximal the first handle and adapted to control contraction of the snare and cauterization. The handles are coupled by a tubular sheath extension.
The physician""s handle is preferably positioned along the sheath of the snare instrument so that it is a few inches proximal to the entry port of the endoscope handle when the distal end of the sheath is adjacent to the distal end of an endoscope. The physician""s handle serves as a grippable element on the sheath and contains a rotating means for rotating the shaft, so that when the physician grips that handle the physician is capable of steering (rotating) the snare by operating the rotating means. In addition, the physician is also capable of positioning the entire sheath relative to the endoscope by sliding the sheath into and out of the working channel of the endoscope. The proximal handle is operable by an assistant and permits longitudinal movement of the shaft and snare and the application of a cautery current to the shaft and snare.
According to other embodiments, the snare instrument is provided with a connector which enables the snare instrument to be fixed relative to an endoscope handle. Additionally, an embodiment is also provided in which a single handle provides a physician with means for advancing and retracting the sheath of the snare instrument relative to the distal end of the endoscope, means for actuating or advancing (opening) and retracting (closing) the snare relative to the distal end of the sheath, and means for steering (rotating) the snare to position the snare over a polyp. Since the physician has direct and immediate control of the entire instrument, the snare instrument obviates the need for an assistant during the procedure, and improves the speed and efficiency of the polypectomy procedure.
In a preferred embodiment, the snare is coupled to or formed at the distal end of the shaft. Preferably, the snare is coupled to the shaft by a crimp band. In an exemplary embodiment a coupling member, for example a shrink tube, is disposed at the distal end of the shaft. The coupling member can be, for example, adhered to the shaft over the crimp band so that when the snare is actuated (e.g., retracted), the coupling member forms a gentle transition between the outer diameter of the shaft and the inner diameter of the sheath. Preferably, the coupling member increases the ability to actuate and end effector, for example, a snare. In an alternate embodiment, the coupling member can be adhered to the shaft just proximal of the crimp band so as to minimize the step in diameter when the snare is retracted.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.